FLAGSTAFF, Ariz. (AP) -- Congress did not intend to reserve water rights for state trust lands, the Arizona Supreme Court ruled Wednesday in settling a question important to resolving claims to the Little Colorado and Gila rivers.

State officials had argued that when Congress granted the land to Arizona for universities, government buildings, prisons and other institutions, it established a trust similar to creating reservations for American Indian tribes and, therefore, implied reserved water rights.

The high court said land grants are different in that they are not the product of negotiated agreements or treaties. It also rejected Arizona's argument that Congress meant to reserve water rights for state trust lands because lawmakers were aware that water was needed to make use of the arid land.

"Support of the common schools and other specific institutions undoubtedly serves the public interest," the court wrote in its ruling. "It is not, however, a federal purpose."

Arizona became a state in 1912, carved out of what once was New Mexico territory. Two-thirds of the more than 9 million acres of state trust lands lie in the river basins.

The state had filed motions for partial summary judgment in two cases -- one in Maricopa County Superior Court to resolve Gila River claims and the other in Apache County Superior Court for the Little Colorado River. The state appealed a determination from the water judge overseeing both cases that federal reserved water rights don't apply to state trust lands.

Supreme Court Justice A. John Pelander, writing for the court, said Congress compensated Arizona for the relatively low value of the land granted by giving the state more land. Although a federal law that set requirements for Arizona and New Mexico territories to become states imposes enforceable trust obligations on Arizona, it doesn't allow the federal government to make policy decisions on how state institutions are run, the court said.

The New Mexico Supreme Court ruled similarly in a case involving rights to the San Juan River.

The Arizona State Land Department said a determination in the state's favor would have upped the value of the lands held in trust for public education and furthered the department's ability to generate revenue. Department spokeswoman Vanessa Hickman said it would continue to pursue its water claims in the court.

Arizona's argument had posed a serious threat to tribes, cities and farmers, who are among those participating in court proceedings to resolve rights to water from the two rivers, said University of Arizona regents' professor Robert Glennon. Nearly 10,000 claims have been staked in the cases that has been ongoing for decades.

"There are more than 9 million acres of state trust lands. If suddenly these lands had water rights, they would overwhelm all other uses of water," said Glennon, author of the book, "Unquenchable: America's Water Crisis and What To Do About It."

Congress never explicitly reserved water rights for federal reservations, but they've been implied in the creation of federal reservations for American Indians, military bases, and national forests, parks and monuments. The U.S. Supreme Court repeatedly has recognized those rights.

Congress defers to state water law except in limited circumstances, such as water rights for federal reservations, said water rights attorney Stanley Pollack, who works for the Navajo Nation.

In the Gila River case, for example, the parties are wrangling over water rights for the Army's Fort Huachuca base in southern Arizona, which has federally reserved water rights.

The Navajo and Hopi tribes recently took up a settlement agreement that would have resolved claims to the Little Colorado River basin, but they've returned to litigation after Navajo lawmakers rejected it. Aside from Zuni Pueblo, no other Arizona tribe has acquired rights to the Little Colorado River.

Pollack said the Arizona justices' ruling "removes an important cloud that hovers over everyone's water rights in both cases."

Dave Roberts, water resource manager for the Salt River Project, said the state Supreme Court made the right decision.

"The opposite decisions could have thrown a huge monkey wrench into the state's water allocation process and raised still more uncertainty for water users," he said.